1<!DOCTYPE html> 2<html lang="en"> 3<head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <meta name="nodejs.org:node-version" content="v14.19.1"> 7 <title>DNS | Node.js v14.19.1 Documentation</title> 8 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> 9 <link rel="stylesheet" href="assets/style.css"> 10 <link rel="stylesheet" href="assets/hljs.css"> 11 <link rel="canonical" href="https://nodejs.org/api/dns.html"> 12</head> 13<body class="alt apidoc" id="api-section-dns"> 14 <div id="content" class="clearfix"> 15 <div id="column2" class="interior"> 16 <div id="intro" class="interior"> 17 <a href="/" title="Go back to the home page"> 18 Node.js 19 </a> 20 </div> 21 <ul> 22<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 23<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 24</ul> 25<hr class="line"> 26<ul> 27<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 28<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 29<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 30<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 31<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 32<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 33<li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 34<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 35<li><a href="cli.html" class="nav-cli">Command-line options</a></li> 36<li><a href="console.html" class="nav-console">Console</a></li> 37<li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 38<li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 39<li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 40<li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> 41<li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> 42<li><a href="dns.html" class="nav-dns active">DNS</a></li> 43<li><a href="domain.html" class="nav-domain">Domain</a></li> 44<li><a href="errors.html" class="nav-errors">Errors</a></li> 45<li><a href="events.html" class="nav-events">Events</a></li> 46<li><a href="fs.html" class="nav-fs">File system</a></li> 47<li><a href="globals.html" class="nav-globals">Globals</a></li> 48<li><a href="http.html" class="nav-http">HTTP</a></li> 49<li><a href="http2.html" class="nav-http2">HTTP/2</a></li> 50<li><a href="https.html" class="nav-https">HTTPS</a></li> 51<li><a href="inspector.html" class="nav-inspector">Inspector</a></li> 52<li><a href="intl.html" class="nav-intl">Internationalization</a></li> 53<li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> 54<li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> 55<li><a href="module.html" class="nav-module">Modules: <code>module</code> API</a></li> 56<li><a href="packages.html" class="nav-packages">Modules: Packages</a></li> 57<li><a href="net.html" class="nav-net">Net</a></li> 58<li><a href="os.html" class="nav-os">OS</a></li> 59<li><a href="path.html" class="nav-path">Path</a></li> 60<li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> 61<li><a href="policy.html" class="nav-policy">Policies</a></li> 62<li><a href="process.html" class="nav-process">Process</a></li> 63<li><a href="punycode.html" class="nav-punycode">Punycode</a></li> 64<li><a href="querystring.html" class="nav-querystring">Query strings</a></li> 65<li><a href="readline.html" class="nav-readline">Readline</a></li> 66<li><a href="repl.html" class="nav-repl">REPL</a></li> 67<li><a href="report.html" class="nav-report">Report</a></li> 68<li><a href="stream.html" class="nav-stream">Stream</a></li> 69<li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> 70<li><a href="timers.html" class="nav-timers">Timers</a></li> 71<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 72<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 73<li><a href="tty.html" class="nav-tty">TTY</a></li> 74<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 75<li><a href="url.html" class="nav-url">URL</a></li> 76<li><a href="util.html" class="nav-util">Utilities</a></li> 77<li><a href="v8.html" class="nav-v8">V8</a></li> 78<li><a href="vm.html" class="nav-vm">VM</a></li> 79<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 80<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 81<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 82</ul> 83<hr class="line"> 84<ul> 85<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 86</ul> 87 </div> 88 89 <div id="column1" data-id="dns" class="interior"> 90 <header> 91 <div class="header-container"> 92 <h1>Node.js v14.19.1 documentation</h1> 93 <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 94 <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 95 <path fill="none" d="M0 0h24v24H0z" /> 96 <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 97 <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 98 </svg> 99 <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 100 <path d="M0 0h24v24H0z" fill="none" /> 101 <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 3.91l-1.41-1.41-1.79 1.79 1.41 1.41 1.79-1.79zm-3.21 13.7l1.79 1.8 1.41-1.41-1.8-1.79-1.4 1.4zM20 10.5v2h3v-2h-3zm-8-5c-3.31 0-6 2.69-6 6s2.69 6 6 6 6-2.69 6-6-2.69-6-6-6zm-1 16.95h2V19.5h-2v2.95zm-7.45-3.91l1.41 1.41 1.79-1.8-1.41-1.41-1.79 1.8z"/> 102 </svg> 103 </button> 104 </div> 105 <div id="gtoc"> 106 <ul> 107 <li> 108 <a href="index.html">Index</a> 109 </li> 110 <li> 111 <a href="all.html">View on single page</a> 112 </li> 113 <li> 114 <a href="dns.json">View as JSON</a> 115 </li> 116 117 <li class="version-picker"> 118 <a href="#">View another version <span>▼</span></a> 119 <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v17.x/api/dns.html">17.x</a></li> 120<li><a href="https://nodejs.org/docs/latest-v16.x/api/dns.html">16.x <b>LTS</b></a></li> 121<li><a href="https://nodejs.org/docs/latest-v15.x/api/dns.html">15.x</a></li> 122<li><a href="https://nodejs.org/docs/latest-v14.x/api/dns.html">14.x <b>LTS</b></a></li> 123<li><a href="https://nodejs.org/docs/latest-v13.x/api/dns.html">13.x</a></li> 124<li><a href="https://nodejs.org/docs/latest-v12.x/api/dns.html">12.x <b>LTS</b></a></li> 125<li><a href="https://nodejs.org/docs/latest-v11.x/api/dns.html">11.x</a></li> 126<li><a href="https://nodejs.org/docs/latest-v10.x/api/dns.html">10.x</a></li> 127<li><a href="https://nodejs.org/docs/latest-v9.x/api/dns.html">9.x</a></li> 128<li><a href="https://nodejs.org/docs/latest-v8.x/api/dns.html">8.x</a></li> 129<li><a href="https://nodejs.org/docs/latest-v7.x/api/dns.html">7.x</a></li> 130<li><a href="https://nodejs.org/docs/latest-v6.x/api/dns.html">6.x</a></li> 131<li><a href="https://nodejs.org/docs/latest-v5.x/api/dns.html">5.x</a></li> 132<li><a href="https://nodejs.org/docs/latest-v4.x/api/dns.html">4.x</a></li> 133<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/dns.html">0.12.x</a></li> 134<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/dns.html">0.10.x</a></li></ol> 135 </li> 136 137 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/dns.md">Edit on GitHub</a></li> 138 </ul> 139 </div> 140 <hr> 141 </header> 142 143 <details id="toc" open><summary>Table of contents</summary><ul> 144<li><span class="stability_2"><a href="#dns_dns">DNS</a></span> 145<ul> 146<li><a href="#dns_class_dns_resolver">Class: <code>dns.Resolver</code></a> 147<ul> 148<li><a href="#dns_resolver_options"><code>Resolver([options])</code></a></li> 149<li><a href="#dns_resolver_cancel"><code>resolver.cancel()</code></a></li> 150<li><a href="#dns_resolver_setlocaladdress_ipv4_ipv6"><code>resolver.setLocalAddress([ipv4][, ipv6])</code></a></li> 151</ul> 152</li> 153<li><a href="#dns_dns_getservers"><code>dns.getServers()</code></a></li> 154<li><a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup(hostname[, options], callback)</code></a> 155<ul> 156<li><a href="#dns_supported_getaddrinfo_flags">Supported getaddrinfo flags</a></li> 157</ul> 158</li> 159<li><a href="#dns_dns_lookupservice_address_port_callback"><code>dns.lookupService(address, port, callback)</code></a></li> 160<li><a href="#dns_dns_resolve_hostname_rrtype_callback"><code>dns.resolve(hostname[, rrtype], callback)</code></a></li> 161<li><a href="#dns_dns_resolve4_hostname_options_callback"><code>dns.resolve4(hostname[, options], callback)</code></a></li> 162<li><a href="#dns_dns_resolve6_hostname_options_callback"><code>dns.resolve6(hostname[, options], callback)</code></a></li> 163<li><a href="#dns_dns_resolveany_hostname_callback"><code>dns.resolveAny(hostname, callback)</code></a></li> 164<li><a href="#dns_dns_resolvecname_hostname_callback"><code>dns.resolveCname(hostname, callback)</code></a></li> 165<li><a href="#dns_dns_resolvecaa_hostname_callback"><code>dns.resolveCaa(hostname, callback)</code></a></li> 166<li><a href="#dns_dns_resolvemx_hostname_callback"><code>dns.resolveMx(hostname, callback)</code></a></li> 167<li><a href="#dns_dns_resolvenaptr_hostname_callback"><code>dns.resolveNaptr(hostname, callback)</code></a></li> 168<li><a href="#dns_dns_resolvens_hostname_callback"><code>dns.resolveNs(hostname, callback)</code></a></li> 169<li><a href="#dns_dns_resolveptr_hostname_callback"><code>dns.resolvePtr(hostname, callback)</code></a></li> 170<li><a href="#dns_dns_resolvesoa_hostname_callback"><code>dns.resolveSoa(hostname, callback)</code></a></li> 171<li><a href="#dns_dns_resolvesrv_hostname_callback"><code>dns.resolveSrv(hostname, callback)</code></a></li> 172<li><a href="#dns_dns_resolvetxt_hostname_callback"><code>dns.resolveTxt(hostname, callback)</code></a></li> 173<li><a href="#dns_dns_reverse_ip_callback"><code>dns.reverse(ip, callback)</code></a></li> 174<li><a href="#dns_dns_setdefaultresultorder_order"><code>dns.setDefaultResultOrder(order)</code></a></li> 175<li><a href="#dns_dns_setservers_servers"><code>dns.setServers(servers)</code></a></li> 176<li><a href="#dns_dns_promises_api">DNS promises API</a> 177<ul> 178<li><a href="#dns_class_dnspromises_resolver">Class: <code>dnsPromises.Resolver</code></a></li> 179<li><a href="#dns_resolver_cancel_1"><code>resolver.cancel()</code></a></li> 180<li><a href="#dns_dnspromises_getservers"><code>dnsPromises.getServers()</code></a></li> 181<li><a href="#dns_dnspromises_lookup_hostname_options"><code>dnsPromises.lookup(hostname[, options])</code></a></li> 182<li><a href="#dns_dnspromises_lookupservice_address_port"><code>dnsPromises.lookupService(address, port)</code></a></li> 183<li><a href="#dns_dnspromises_resolve_hostname_rrtype"><code>dnsPromises.resolve(hostname[, rrtype])</code></a></li> 184<li><a href="#dns_dnspromises_resolve4_hostname_options"><code>dnsPromises.resolve4(hostname[, options])</code></a></li> 185<li><a href="#dns_dnspromises_resolve6_hostname_options"><code>dnsPromises.resolve6(hostname[, options])</code></a></li> 186<li><a href="#dns_dnspromises_resolveany_hostname"><code>dnsPromises.resolveAny(hostname)</code></a></li> 187<li><a href="#dns_dnspromises_resolvecaa_hostname"><code>dnsPromises.resolveCaa(hostname)</code></a></li> 188<li><a href="#dns_dnspromises_resolvecname_hostname"><code>dnsPromises.resolveCname(hostname)</code></a></li> 189<li><a href="#dns_dnspromises_resolvemx_hostname"><code>dnsPromises.resolveMx(hostname)</code></a></li> 190<li><a href="#dns_dnspromises_resolvenaptr_hostname"><code>dnsPromises.resolveNaptr(hostname)</code></a></li> 191<li><a href="#dns_dnspromises_resolvens_hostname"><code>dnsPromises.resolveNs(hostname)</code></a></li> 192<li><a href="#dns_dnspromises_resolveptr_hostname"><code>dnsPromises.resolvePtr(hostname)</code></a></li> 193<li><a href="#dns_dnspromises_resolvesoa_hostname"><code>dnsPromises.resolveSoa(hostname)</code></a></li> 194<li><a href="#dns_dnspromises_resolvesrv_hostname"><code>dnsPromises.resolveSrv(hostname)</code></a></li> 195<li><a href="#dns_dnspromises_resolvetxt_hostname"><code>dnsPromises.resolveTxt(hostname)</code></a></li> 196<li><a href="#dns_dnspromises_reverse_ip"><code>dnsPromises.reverse(ip)</code></a></li> 197<li><a href="#dns_dnspromises_setdefaultresultorder_order"><code>dnsPromises.setDefaultResultOrder(order)</code></a></li> 198<li><a href="#dns_dnspromises_setservers_servers"><code>dnsPromises.setServers(servers)</code></a></li> 199</ul> 200</li> 201<li><a href="#dns_error_codes">Error codes</a></li> 202<li><a href="#dns_implementation_considerations">Implementation considerations</a> 203<ul> 204<li><a href="#dns_dns_lookup"><code>dns.lookup()</code></a></li> 205<li><a href="#dns_dns_resolve_dns_resolve_and_dns_reverse"><code>dns.resolve()</code>, <code>dns.resolve*()</code> and <code>dns.reverse()</code></a></li> 206</ul> 207</li> 208</ul> 209</li> 210</ul></details> 211 212 <div id="apicontent"> 213 <h2>DNS<span><a class="mark" href="#dns_dns" id="dns_dns">#</a></span></h2> 214 215<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 216<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v14.19.1/lib/dns.js">lib/dns.js</a></p> 217<p>The <code>dns</code> module enables name resolution. For example, use it to look up IP 218addresses of host names.</p> 219<p>Although named for the <a href="https://en.wikipedia.org/wiki/Domain_Name_System">Domain Name System (DNS)</a>, it does not always use the 220DNS protocol for lookups. <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> uses the operating system 221facilities to perform name resolution. It may not need to perform any network 222communication. To perform name resolution the way other applications on the same 223system do, use <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a>.</p> 224<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>); 225 226dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.org'</span>, <span class="hljs-function">(<span class="hljs-params">err, address, family</span>) =></span> { 227 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'address: %j family: IPv%s'</span>, address, family); 228}); 229<span class="hljs-comment">// address: "93.184.216.34" family: IPv4</span></code></pre> 230<p>All other functions in the <code>dns</code> module connect to an actual DNS server to 231perform name resolution. They will always use the network to perform DNS 232queries. These functions do not use the same set of configuration files used by 233<a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> (e.g. <code>/etc/hosts</code>). Use these functions to always perform 234DNS queries, bypassing other name-resolution facilities.</p> 235<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>); 236 237dns.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'archive.org'</span>, <span class="hljs-function">(<span class="hljs-params">err, addresses</span>) =></span> { 238 <span class="hljs-keyword">if</span> (err) <span class="hljs-keyword">throw</span> err; 239 240 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`addresses: <span class="hljs-subst">${<span class="hljs-built_in">JSON</span>.stringify(addresses)}</span>`</span>); 241 242 addresses.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">a</span>) =></span> { 243 dns.<span class="hljs-title function_">reverse</span>(a, <span class="hljs-function">(<span class="hljs-params">err, hostnames</span>) =></span> { 244 <span class="hljs-keyword">if</span> (err) { 245 <span class="hljs-keyword">throw</span> err; 246 } 247 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`reverse for <span class="hljs-subst">${a}</span>: <span class="hljs-subst">${<span class="hljs-built_in">JSON</span>.stringify(hostnames)}</span>`</span>); 248 }); 249 }); 250});</code></pre> 251<p>See the <a href="#dns_implementation_considerations">Implementation considerations section</a> for more information.</p> 252<section><h3>Class: <code>dns.Resolver</code><span><a class="mark" href="#dns_class_dns_resolver" id="dns_class_dns_resolver">#</a></span></h3> 253<div class="api_metadata"> 254<span>Added in: v8.3.0</span> 255</div> 256<p>An independent resolver for DNS requests.</p> 257<p>Creating a new resolver uses the default server settings. Setting 258the servers used for a resolver using 259<a href="#dns_dns_setservers_servers"><code>resolver.setServers()</code></a> does not affect 260other resolvers:</p> 261<pre><code class="language-js"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">Resolver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>); 262<span class="hljs-keyword">const</span> resolver = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Resolver</span>(); 263resolver.<span class="hljs-title function_">setServers</span>([<span class="hljs-string">'4.4.4.4'</span>]); 264 265<span class="hljs-comment">// This request will use the server at 4.4.4.4, independent of global settings.</span> 266resolver.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'example.org'</span>, <span class="hljs-function">(<span class="hljs-params">err, addresses</span>) =></span> { 267 <span class="hljs-comment">// ...</span> 268});</code></pre> 269<p>The following methods from the <code>dns</code> module are available:</p> 270<ul> 271<li><a href="#dns_dns_getservers"><code>resolver.getServers()</code></a></li> 272<li><a href="#dns_dns_resolve_hostname_rrtype_callback"><code>resolver.resolve()</code></a></li> 273<li><a href="#dns_dns_resolve4_hostname_options_callback"><code>resolver.resolve4()</code></a></li> 274<li><a href="#dns_dns_resolve6_hostname_options_callback"><code>resolver.resolve6()</code></a></li> 275<li><a href="#dns_dns_resolveany_hostname_callback"><code>resolver.resolveAny()</code></a></li> 276<li><a href="#dns_dns_resolvecaa_hostname_callback"><code>resolver.resolveCaa()</code></a></li> 277<li><a href="#dns_dns_resolvecname_hostname_callback"><code>resolver.resolveCname()</code></a></li> 278<li><a href="#dns_dns_resolvemx_hostname_callback"><code>resolver.resolveMx()</code></a></li> 279<li><a href="#dns_dns_resolvenaptr_hostname_callback"><code>resolver.resolveNaptr()</code></a></li> 280<li><a href="#dns_dns_resolvens_hostname_callback"><code>resolver.resolveNs()</code></a></li> 281<li><a href="#dns_dns_resolveptr_hostname_callback"><code>resolver.resolvePtr()</code></a></li> 282<li><a href="#dns_dns_resolvesoa_hostname_callback"><code>resolver.resolveSoa()</code></a></li> 283<li><a href="#dns_dns_resolvesrv_hostname_callback"><code>resolver.resolveSrv()</code></a></li> 284<li><a href="#dns_dns_resolvetxt_hostname_callback"><code>resolver.resolveTxt()</code></a></li> 285<li><a href="#dns_dns_reverse_ip_callback"><code>resolver.reverse()</code></a></li> 286<li><a href="#dns_dns_setservers_servers"><code>resolver.setServers()</code></a></li> 287</ul> 288<h4><code>Resolver([options])</code><span><a class="mark" href="#dns_resolver_options" id="dns_resolver_options">#</a></span></h4> 289<div class="api_metadata"> 290<details class="changelog"><summary>History</summary> 291<table> 292<tbody><tr><th>Version</th><th>Changes</th></tr> 293<tr><td>v14.18.0</td> 294<td><p>The <code>options</code> object now accepts a <code>tries</code> option.</p></td></tr> 295<tr><td>v14.5.0</td> 296<td><p>The constructor now accepts an <code>options</code> object. The single supported option is <code>timeout</code>.</p></td></tr> 297<tr><td>v8.3.0</td> 298<td><p><span>Added in: v8.3.0</span></p></td></tr> 299</tbody></table> 300</details> 301</div> 302<p>Create a new resolver.</p> 303<ul> 304<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 305<ul> 306<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Query timeout in milliseconds, or <code>-1</code> to use the 307default timeout.</li> 308<li><code>tries</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The number of tries the resolver will try contacting 309each name server before giving up. <strong>Default:</strong> <code>4</code></li> 310</ul> 311</li> 312</ul> 313<h4><code>resolver.cancel()</code><span><a class="mark" href="#dns_resolver_cancel" id="dns_resolver_cancel">#</a></span></h4> 314<div class="api_metadata"> 315<span>Added in: v8.3.0</span> 316</div> 317<p>Cancel all outstanding DNS queries made by this resolver. The corresponding 318callbacks will be called with an error with code <code>ECANCELLED</code>.</p> 319<h4><code>resolver.setLocalAddress([ipv4][, ipv6])</code><span><a class="mark" href="#dns_resolver_setlocaladdress_ipv4_ipv6" id="dns_resolver_setlocaladdress_ipv4_ipv6">#</a></span></h4> 320<div class="api_metadata"> 321<span>Added in: v14.17.0</span> 322</div> 323<ul> 324<li><code>ipv4</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string representation of an IPv4 address. 325<strong>Default:</strong> <code>'0.0.0.0'</code></li> 326<li><code>ipv6</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string representation of an IPv6 address. 327<strong>Default:</strong> <code>'::0'</code></li> 328</ul> 329<p>The resolver instance will send its requests from the specified IP address. 330This allows programs to specify outbound interfaces when used on multi-homed 331systems.</p> 332<p>If a v4 or v6 address is not specified, it is set to the default, and the 333operating system will choose a local address automatically.</p> 334<p>The resolver will use the v4 local address when making requests to IPv4 DNS 335servers, and the v6 local address when making requests to IPv6 DNS servers. 336The <code>rrtype</code> of resolution requests has no impact on the local address used.</p> 337</section><section><h3><code>dns.getServers()</code><span><a class="mark" href="#dns_dns_getservers" id="dns_dns_getservers">#</a></span></h3> 338<div class="api_metadata"> 339<span>Added in: v0.11.3</span> 340</div> 341<ul> 342<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 343</ul> 344<p>Returns an array of IP address strings, formatted according to <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a>, 345that are currently configured for DNS resolution. A string will include a port 346section if a custom port is used.</p> 347<!-- eslint-disable semi--> 348<pre><code class="language-js">[ 349 <span class="hljs-string">'4.4.4.4'</span>, 350 <span class="hljs-string">'2001:4860:4860::8888'</span>, 351 <span class="hljs-string">'4.4.4.4:1053'</span>, 352 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 353]</code></pre> 354</section><section><h3><code>dns.lookup(hostname[, options], callback)</code><span><a class="mark" href="#dns_dns_lookup_hostname_options_callback" id="dns_dns_lookup_hostname_options_callback">#</a></span></h3> 355<div class="api_metadata"> 356<details class="changelog"><summary>History</summary> 357<table> 358<tbody><tr><th>Version</th><th>Changes</th></tr> 359<tr><td>v8.5.0</td> 360<td><p>The <code>verbatim</code> option is supported now.</p></td></tr> 361<tr><td>v1.2.0</td> 362<td><p>The <code>all</code> option is supported now.</p></td></tr> 363<tr><td>v0.1.90</td> 364<td><p><span>Added in: v0.1.90</span></p></td></tr> 365</tbody></table> 366</details> 367</div> 368<ul> 369<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 370<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 371<ul> 372<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The record family. Must be <code>4</code>, <code>6</code>, or <code>0</code>. The value 373<code>0</code> indicates that IPv4 and IPv6 addresses are both returned. <strong>Default:</strong> 374<code>0</code>.</li> 375<li><code>hints</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> One or more <a href="#dns_supported_getaddrinfo_flags">supported <code>getaddrinfo</code> flags</a>. Multiple 376flags may be passed by bitwise <code>OR</code>ing their values.</li> 377<li><code>all</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the callback returns all resolved addresses in 378an array. Otherwise, returns a single address. <strong>Default:</strong> <code>false</code>.</li> 379<li><code>verbatim</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the callback receives IPv4 and IPv6 380addresses in the order the DNS resolver returned them. When <code>false</code>, 381IPv4 addresses are placed before IPv6 addresses. 382<strong>Default:</strong> currently <code>false</code> (addresses are reordered) but this is 383expected to change in the not too distant future. Default value is 384configurable using <a href="#dns_dns_setdefaultresultorder_order"><code>dns.setDefaultResultOrder()</code></a> or 385<a href="cli.html#cli_dns_result_order_order"><code>--dns-result-order</code></a>. New code should use <code>{ verbatim: true }</code>.</li> 386</ul> 387</li> 388<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 389<ul> 390<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 391<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string representation of an IPv4 or IPv6 address.</li> 392<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>4</code> or <code>6</code>, denoting the family of <code>address</code>, or <code>0</code> if 393the address is not an IPv4 or IPv6 address. <code>0</code> is a likely indicator of a 394bug in the name resolution service used by the operating system.</li> 395</ul> 396</li> 397</ul> 398<p>Resolves a host name (e.g. <code>'nodejs.org'</code>) into the first found A (IPv4) or 399AAAA (IPv6) record. All <code>option</code> properties are optional. If <code>options</code> is an 400integer, then it must be <code>4</code> or <code>6</code> – if <code>options</code> is not provided, then IPv4 401and IPv6 addresses are both returned if found.</p> 402<p>With the <code>all</code> option set to <code>true</code>, the arguments for <code>callback</code> change to 403<code>(err, addresses)</code>, with <code>addresses</code> being an array of objects with the 404properties <code>address</code> and <code>family</code>.</p> 405<p>On error, <code>err</code> is an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> is the error code. 406Keep in mind that <code>err.code</code> will be set to <code>'ENOTFOUND'</code> not only when 407the host name does not exist but also when the lookup fails in other ways 408such as no available file descriptors.</p> 409<p><code>dns.lookup()</code> does not necessarily have anything to do with the DNS protocol. 410The implementation uses an operating system facility that can associate names 411with addresses, and vice versa. This implementation can have subtle but 412important consequences on the behavior of any Node.js program. Please take some 413time to consult the <a href="#dns_implementation_considerations">Implementation considerations section</a> before using 414<code>dns.lookup()</code>.</p> 415<p>Example usage:</p> 416<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>); 417<span class="hljs-keyword">const</span> options = { 418 <span class="hljs-attr">family</span>: <span class="hljs-number">6</span>, 419 <span class="hljs-attr">hints</span>: dns.<span class="hljs-property">ADDRCONFIG</span> | dns.<span class="hljs-property">V4MAPPED</span>, 420}; 421dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options, <span class="hljs-function">(<span class="hljs-params">err, address, family</span>) =></span> 422 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'address: %j family: IPv%s'</span>, address, family)); 423<span class="hljs-comment">// address: "2606:2800:220:1:248:1893:25c8:1946" family: IPv6</span> 424 425<span class="hljs-comment">// When options.all is true, the result will be an Array.</span> 426options.<span class="hljs-property">all</span> = <span class="hljs-literal">true</span>; 427dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options, <span class="hljs-function">(<span class="hljs-params">err, addresses</span>) =></span> 428 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'addresses: %j'</span>, addresses)); 429<span class="hljs-comment">// addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]</span></code></pre> 430<p>If this method is invoked as its <a href="util.html#util_util_promisify_original"><code>util.promisify()</code></a>ed version, and <code>all</code> 431is not set to <code>true</code>, it returns a <code>Promise</code> for an <code>Object</code> with <code>address</code> and 432<code>family</code> properties.</p> 433<h4>Supported getaddrinfo flags<span><a class="mark" href="#dns_supported_getaddrinfo_flags" id="dns_supported_getaddrinfo_flags">#</a></span></h4> 434<div class="api_metadata"> 435<details class="changelog"><summary>History</summary> 436<table> 437<tbody><tr><th>Version</th><th>Changes</th></tr> 438<tr><td>v14.0.0</td> 439<td><p>Added support for the <code>dns.ALL</code> flag.</p></td></tr> 440</tbody></table> 441</details> 442</div> 443<p>The following flags can be passed as hints to <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a>.</p> 444<ul> 445<li><code>dns.ADDRCONFIG</code>: Limits returned address types to the types of non-loopback 446addresses configured on the system. For example, IPv4 addresses are only 447returned if the current system has at least one IPv4 address configured.</li> 448<li><code>dns.V4MAPPED</code>: If the IPv6 family was specified, but no IPv6 addresses were 449found, then return IPv4 mapped IPv6 addresses. It is not supported 450on some operating systems (e.g FreeBSD 10.1).</li> 451<li><code>dns.ALL</code>: If <code>dns.V4MAPPED</code> is specified, return resolved IPv6 addresses as 452well as IPv4 mapped IPv6 addresses.</li> 453</ul> 454</section><section><h3><code>dns.lookupService(address, port, callback)</code><span><a class="mark" href="#dns_dns_lookupservice_address_port_callback" id="dns_dns_lookupservice_address_port_callback">#</a></span></h3> 455<div class="api_metadata"> 456<span>Added in: v0.11.14</span> 457</div> 458<ul> 459<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 460<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 461<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 462<ul> 463<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 464<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> e.g. <code>example.com</code></li> 465<li><code>service</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> e.g. <code>http</code></li> 466</ul> 467</li> 468</ul> 469<p>Resolves the given <code>address</code> and <code>port</code> into a host name and service using 470the operating system's underlying <code>getnameinfo</code> implementation.</p> 471<p>If <code>address</code> is not a valid IP address, a <code>TypeError</code> will be thrown. 472The <code>port</code> will be coerced to a number. If it is not a legal port, a <code>TypeError</code> 473will be thrown.</p> 474<p>On an error, <code>err</code> is an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> is the error code.</p> 475<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>); 476dns.<span class="hljs-title function_">lookupService</span>(<span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-number">22</span>, <span class="hljs-function">(<span class="hljs-params">err, hostname, service</span>) =></span> { 477 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(hostname, service); 478 <span class="hljs-comment">// Prints: localhost ssh</span> 479});</code></pre> 480<p>If this method is invoked as its <a href="util.html#util_util_promisify_original"><code>util.promisify()</code></a>ed version, it returns a 481<code>Promise</code> for an <code>Object</code> with <code>hostname</code> and <code>service</code> properties.</p> 482</section><section><h3><code>dns.resolve(hostname[, rrtype], callback)</code><span><a class="mark" href="#dns_dns_resolve_hostname_rrtype_callback" id="dns_dns_resolve_hostname_rrtype_callback">#</a></span></h3> 483<div class="api_metadata"> 484<span>Added in: v0.1.27</span> 485</div> 486<ul> 487<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 488<li><code>rrtype</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Resource record type. <strong>Default:</strong> <code>'A'</code>.</li> 489<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 490<ul> 491<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 492<li><code>records</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 493</ul> 494</li> 495</ul> 496<p>Uses the DNS protocol to resolve a host name (e.g. <code>'nodejs.org'</code>) into an array 497of the resource records. The <code>callback</code> function has arguments 498<code>(err, records)</code>. When successful, <code>records</code> will be an array of resource 499records. The type and structure of individual results varies based on <code>rrtype</code>:</p> 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583<table><thead><tr><th><code>rrtype</code></th><th><code>records</code> contains</th><th>Result type</th><th>Shorthand method</th></tr></thead><tbody><tr><td><code>'A'</code></td><td>IPv4 addresses (default)</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dns_resolve4_hostname_options_callback"><code>dns.resolve4()</code></a></td></tr><tr><td><code>'AAAA'</code></td><td>IPv6 addresses</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dns_resolve6_hostname_options_callback"><code>dns.resolve6()</code></a></td></tr><tr><td><code>'ANY'</code></td><td>any records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dns_resolveany_hostname_callback"><code>dns.resolveAny()</code></a></td></tr><tr><td><code>'CAA'</code></td><td>CA authorization records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dns_resolvecaa_hostname_callback"><code>dns.resolveCaa()</code></a></td></tr><tr><td><code>'CNAME'</code></td><td>canonical name records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dns_resolvecname_hostname_callback"><code>dns.resolveCname()</code></a></td></tr><tr><td><code>'MX'</code></td><td>mail exchange records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dns_resolvemx_hostname_callback"><code>dns.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>name authority pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dns_resolvenaptr_hostname_callback"><code>dns.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td>name server records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dns_resolvens_hostname_callback"><code>dns.resolveNs()</code></a></td></tr><tr><td><code>'PTR'</code></td><td>pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dns_resolveptr_hostname_callback"><code>dns.resolvePtr()</code></a></td></tr><tr><td><code>'SOA'</code></td><td>start of authority records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dns_resolvesoa_hostname_callback"><code>dns.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>service records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dns_resolvesrv_hostname_callback"><code>dns.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>text records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></td><td><a href="#dns_dns_resolvetxt_hostname_callback"><code>dns.resolveTxt()</code></a></td></tr></tbody></table> 584<p>On error, <code>err</code> is an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> is one of the 585<a href="#dns_error_codes">DNS error codes</a>.</p> 586</section><section><h3><code>dns.resolve4(hostname[, options], callback)</code><span><a class="mark" href="#dns_dns_resolve4_hostname_options_callback" id="dns_dns_resolve4_hostname_options_callback">#</a></span></h3> 587<div class="api_metadata"> 588<details class="changelog"><summary>History</summary> 589<table> 590<tbody><tr><th>Version</th><th>Changes</th></tr> 591<tr><td>v7.2.0</td> 592<td><p>This method now supports passing <code>options</code>, specifically <code>options.ttl</code>.</p></td></tr> 593<tr><td>v0.1.16</td> 594<td><p><span>Added in: v0.1.16</span></p></td></tr> 595</tbody></table> 596</details> 597</div> 598<ul> 599<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 600<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 601<ul> 602<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 603When <code>true</code>, the callback receives an array of 604<code>{ address: '1.2.3.4', ttl: 60 }</code> objects rather than an array of strings, 605with the TTL expressed in seconds.</li> 606</ul> 607</li> 608<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 609<ul> 610<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 611<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 612</ul> 613</li> 614</ul> 615<p>Uses the DNS protocol to resolve a IPv4 addresses (<code>A</code> records) for the 616<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function 617will contain an array of IPv4 addresses (e.g. 618<code>['74.125.79.104', '74.125.79.105', '74.125.79.106']</code>).</p> 619</section><section><h3><code>dns.resolve6(hostname[, options], callback)</code><span><a class="mark" href="#dns_dns_resolve6_hostname_options_callback" id="dns_dns_resolve6_hostname_options_callback">#</a></span></h3> 620<div class="api_metadata"> 621<details class="changelog"><summary>History</summary> 622<table> 623<tbody><tr><th>Version</th><th>Changes</th></tr> 624<tr><td>v7.2.0</td> 625<td><p>This method now supports passing <code>options</code>, specifically <code>options.ttl</code>.</p></td></tr> 626<tr><td>v0.1.16</td> 627<td><p><span>Added in: v0.1.16</span></p></td></tr> 628</tbody></table> 629</details> 630</div> 631<ul> 632<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 633<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 634<ul> 635<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 636When <code>true</code>, the callback receives an array of 637<code>{ address: '0:1:2:3:4:5:6:7', ttl: 60 }</code> objects rather than an array of 638strings, with the TTL expressed in seconds.</li> 639</ul> 640</li> 641<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 642<ul> 643<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 644<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 645</ul> 646</li> 647</ul> 648<p>Uses the DNS protocol to resolve a IPv6 addresses (<code>AAAA</code> records) for the 649<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function 650will contain an array of IPv6 addresses.</p> 651</section><section><h3><code>dns.resolveAny(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolveany_hostname_callback" id="dns_dns_resolveany_hostname_callback">#</a></span></h3> 652<ul> 653<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 654<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 655<ul> 656<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 657<li><code>ret</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 658</ul> 659</li> 660</ul> 661<p>Uses the DNS protocol to resolve all records (also known as <code>ANY</code> or <code>*</code> query). 662The <code>ret</code> argument passed to the <code>callback</code> function will be an array containing 663various types of records. Each object has a property <code>type</code> that indicates the 664type of the current record. And depending on the <code>type</code>, additional properties 665will be present on the object:</p> 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715<table><thead><tr><th>Type</th><th>Properties</th></tr></thead><tbody><tr><td><code>'A'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'AAAA'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'CNAME'</code></td><td><code>value</code></td></tr><tr><td><code>'MX'</code></td><td>Refer to <a href="#dns_dns_resolvemx_hostname_callback"><code>dns.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>Refer to <a href="#dns_dns_resolvenaptr_hostname_callback"><code>dns.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td><code>value</code></td></tr><tr><td><code>'PTR'</code></td><td><code>value</code></td></tr><tr><td><code>'SOA'</code></td><td>Refer to <a href="#dns_dns_resolvesoa_hostname_callback"><code>dns.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>Refer to <a href="#dns_dns_resolvesrv_hostname_callback"><code>dns.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>This type of record contains an array property called <code>entries</code> which refers to <a href="#dns_dns_resolvetxt_hostname_callback"><code>dns.resolveTxt()</code></a>, e.g. <code>{ entries: ['...'], type: 'TXT' }</code></td></tr></tbody></table> 716<p>Here is an example of the <code>ret</code> object passed to the callback:</p> 717<!-- eslint-disable semi --> 718<pre><code class="language-js">[ { <span class="hljs-attr">type</span>: <span class="hljs-string">'A'</span>, <span class="hljs-attr">address</span>: <span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-attr">ttl</span>: <span class="hljs-number">299</span> }, 719 { <span class="hljs-attr">type</span>: <span class="hljs-string">'CNAME'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'example.com'</span> }, 720 { <span class="hljs-attr">type</span>: <span class="hljs-string">'MX'</span>, <span class="hljs-attr">exchange</span>: <span class="hljs-string">'alt4.aspmx.l.example.com'</span>, <span class="hljs-attr">priority</span>: <span class="hljs-number">50</span> }, 721 { <span class="hljs-attr">type</span>: <span class="hljs-string">'NS'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'ns1.example.com'</span> }, 722 { <span class="hljs-attr">type</span>: <span class="hljs-string">'TXT'</span>, <span class="hljs-attr">entries</span>: [ <span class="hljs-string">'v=spf1 include:_spf.example.com ~all'</span> ] }, 723 { <span class="hljs-attr">type</span>: <span class="hljs-string">'SOA'</span>, 724 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns1.example.com'</span>, 725 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'admin.example.com'</span>, 726 <span class="hljs-attr">serial</span>: <span class="hljs-number">156696742</span>, 727 <span class="hljs-attr">refresh</span>: <span class="hljs-number">900</span>, 728 <span class="hljs-attr">retry</span>: <span class="hljs-number">900</span>, 729 <span class="hljs-attr">expire</span>: <span class="hljs-number">1800</span>, 730 <span class="hljs-attr">minttl</span>: <span class="hljs-number">60</span> } ]</code></pre> 731<p>DNS server operators may choose not to respond to <code>ANY</code> 732queries. It may be better to call individual methods like <a href="#dns_dns_resolve4_hostname_options_callback"><code>dns.resolve4()</code></a>, 733<a href="#dns_dns_resolvemx_hostname_callback"><code>dns.resolveMx()</code></a>, and so on. For more details, see <a href="https://tools.ietf.org/html/rfc8482">RFC 8482</a>.</p> 734</section><section><h3><code>dns.resolveCname(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvecname_hostname_callback" id="dns_dns_resolvecname_hostname_callback">#</a></span></h3> 735<div class="api_metadata"> 736<span>Added in: v0.3.2</span> 737</div> 738<ul> 739<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 740<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 741<ul> 742<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 743<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 744</ul> 745</li> 746</ul> 747<p>Uses the DNS protocol to resolve <code>CNAME</code> records for the <code>hostname</code>. The 748<code>addresses</code> argument passed to the <code>callback</code> function 749will contain an array of canonical name records available for the <code>hostname</code> 750(e.g. <code>['bar.example.com']</code>).</p> 751</section><section><h3><code>dns.resolveCaa(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvecaa_hostname_callback" id="dns_dns_resolvecaa_hostname_callback">#</a></span></h3> 752<div class="api_metadata"> 753<span>Added in: v14.17.0</span> 754</div> 755<ul> 756<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 757<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 758<ul> 759<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 760<li><code>records</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 761</ul> 762</li> 763</ul> 764<p>Uses the DNS protocol to resolve <code>CAA</code> records for the <code>hostname</code>. The 765<code>addresses</code> argument passed to the <code>callback</code> function 766will contain an array of certification authority authorization records 767available for the <code>hostname</code> (e.g. <code>[{critical: 0, iodef: 'mailto:pki@example.com'}, {critical: 128, issue: 'pki.example.com'}]</code>).</p> 768</section><section><h3><code>dns.resolveMx(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvemx_hostname_callback" id="dns_dns_resolvemx_hostname_callback">#</a></span></h3> 769<div class="api_metadata"> 770<span>Added in: v0.1.27</span> 771</div> 772<ul> 773<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 774<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 775<ul> 776<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 777<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 778</ul> 779</li> 780</ul> 781<p>Uses the DNS protocol to resolve mail exchange records (<code>MX</code> records) for the 782<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 783contain an array of objects containing both a <code>priority</code> and <code>exchange</code> 784property (e.g. <code>[{priority: 10, exchange: 'mx.example.com'}, ...]</code>).</p> 785</section><section><h3><code>dns.resolveNaptr(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvenaptr_hostname_callback" id="dns_dns_resolvenaptr_hostname_callback">#</a></span></h3> 786<div class="api_metadata"> 787<span>Added in: v0.9.12</span> 788</div> 789<ul> 790<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 791<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 792<ul> 793<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 794<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 795</ul> 796</li> 797</ul> 798<p>Uses the DNS protocol to resolve regular expression based records (<code>NAPTR</code> 799records) for the <code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> 800function will contain an array of objects with the following properties:</p> 801<ul> 802<li><code>flags</code></li> 803<li><code>service</code></li> 804<li><code>regexp</code></li> 805<li><code>replacement</code></li> 806<li><code>order</code></li> 807<li><code>preference</code></li> 808</ul> 809<!-- eslint-skip --> 810<pre><code class="language-js">{ 811 <span class="hljs-attr">flags</span>: <span class="hljs-string">'s'</span>, 812 <span class="hljs-attr">service</span>: <span class="hljs-string">'SIP+D2U'</span>, 813 <span class="hljs-attr">regexp</span>: <span class="hljs-string">''</span>, 814 <span class="hljs-attr">replacement</span>: <span class="hljs-string">'_sip._udp.example.com'</span>, 815 <span class="hljs-attr">order</span>: <span class="hljs-number">30</span>, 816 <span class="hljs-attr">preference</span>: <span class="hljs-number">100</span> 817}</code></pre> 818</section><section><h3><code>dns.resolveNs(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvens_hostname_callback" id="dns_dns_resolvens_hostname_callback">#</a></span></h3> 819<div class="api_metadata"> 820<span>Added in: v0.1.90</span> 821</div> 822<ul> 823<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 824<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 825<ul> 826<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 827<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 828</ul> 829</li> 830</ul> 831<p>Uses the DNS protocol to resolve name server records (<code>NS</code> records) for the 832<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 833contain an array of name server records available for <code>hostname</code> 834(e.g. <code>['ns1.example.com', 'ns2.example.com']</code>).</p> 835</section><section><h3><code>dns.resolvePtr(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolveptr_hostname_callback" id="dns_dns_resolveptr_hostname_callback">#</a></span></h3> 836<div class="api_metadata"> 837<span>Added in: v6.0.0</span> 838</div> 839<ul> 840<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 841<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 842<ul> 843<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 844<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 845</ul> 846</li> 847</ul> 848<p>Uses the DNS protocol to resolve pointer records (<code>PTR</code> records) for the 849<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 850be an array of strings containing the reply records.</p> 851</section><section><h3><code>dns.resolveSoa(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvesoa_hostname_callback" id="dns_dns_resolvesoa_hostname_callback">#</a></span></h3> 852<div class="api_metadata"> 853<span>Added in: v0.11.10</span> 854</div> 855<ul> 856<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 857<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 858<ul> 859<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 860<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 861</ul> 862</li> 863</ul> 864<p>Uses the DNS protocol to resolve a start of authority record (<code>SOA</code> record) for 865the <code>hostname</code>. The <code>address</code> argument passed to the <code>callback</code> function will 866be an object with the following properties:</p> 867<ul> 868<li><code>nsname</code></li> 869<li><code>hostmaster</code></li> 870<li><code>serial</code></li> 871<li><code>refresh</code></li> 872<li><code>retry</code></li> 873<li><code>expire</code></li> 874<li><code>minttl</code></li> 875</ul> 876<!-- eslint-skip --> 877<pre><code class="language-js">{ 878 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns.example.com'</span>, 879 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'root.example.com'</span>, 880 <span class="hljs-attr">serial</span>: <span class="hljs-number">2013101809</span>, 881 <span class="hljs-attr">refresh</span>: <span class="hljs-number">10000</span>, 882 <span class="hljs-attr">retry</span>: <span class="hljs-number">2400</span>, 883 <span class="hljs-attr">expire</span>: <span class="hljs-number">604800</span>, 884 <span class="hljs-attr">minttl</span>: <span class="hljs-number">3600</span> 885}</code></pre> 886</section><section><h3><code>dns.resolveSrv(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvesrv_hostname_callback" id="dns_dns_resolvesrv_hostname_callback">#</a></span></h3> 887<div class="api_metadata"> 888<span>Added in: v0.1.27</span> 889</div> 890<ul> 891<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 892<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 893<ul> 894<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 895<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 896</ul> 897</li> 898</ul> 899<p>Uses the DNS protocol to resolve service records (<code>SRV</code> records) for the 900<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 901be an array of objects with the following properties:</p> 902<ul> 903<li><code>priority</code></li> 904<li><code>weight</code></li> 905<li><code>port</code></li> 906<li><code>name</code></li> 907</ul> 908<!-- eslint-skip --> 909<pre><code class="language-js">{ 910 <span class="hljs-attr">priority</span>: <span class="hljs-number">10</span>, 911 <span class="hljs-attr">weight</span>: <span class="hljs-number">5</span>, 912 <span class="hljs-attr">port</span>: <span class="hljs-number">21223</span>, 913 <span class="hljs-attr">name</span>: <span class="hljs-string">'service.example.com'</span> 914}</code></pre> 915</section><section><h3><code>dns.resolveTxt(hostname, callback)</code><span><a class="mark" href="#dns_dns_resolvetxt_hostname_callback" id="dns_dns_resolvetxt_hostname_callback">#</a></span></h3> 916<div class="api_metadata"> 917<span>Added in: v0.1.27</span> 918</div> 919<!--lint disable no-undefined-references list-item-bullet-indent--> 920<ul> 921<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 922<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 923<ul> 924<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 925<li><code>records</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[][]></a></li> 926</ul> 927</li> 928</ul> 929<!--lint enable no-undefined-references list-item-bullet-indent--> 930<p>Uses the DNS protocol to resolve text queries (<code>TXT</code> records) for the 931<code>hostname</code>. The <code>records</code> argument passed to the <code>callback</code> function is a 932two-dimensional array of the text records available for <code>hostname</code> (e.g. 933<code>[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]</code>). Each sub-array contains TXT chunks of 934one record. Depending on the use case, these could be either joined together or 935treated separately.</p> 936</section><section><h3><code>dns.reverse(ip, callback)</code><span><a class="mark" href="#dns_dns_reverse_ip_callback" id="dns_dns_reverse_ip_callback">#</a></span></h3> 937<div class="api_metadata"> 938<span>Added in: v0.1.16</span> 939</div> 940<ul> 941<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 942<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 943<ul> 944<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 945<li><code>hostnames</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 946</ul> 947</li> 948</ul> 949<p>Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an 950array of host names.</p> 951<p>On error, <code>err</code> is an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> is 952one of the <a href="#dns_error_codes">DNS error codes</a>.</p> 953</section><section><h3><code>dns.setDefaultResultOrder(order)</code><span><a class="mark" href="#dns_dns_setdefaultresultorder_order" id="dns_dns_setdefaultresultorder_order">#</a></span></h3> 954<div class="api_metadata"> 955<span>Added in: v14.18.0</span> 956</div> 957<ul> 958<li><code>order</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> must be <code>'ipv4first'</code> or <code>'verbatim'</code>.</li> 959</ul> 960<p>Set the default value of <code>verbatim</code> in <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> and 961<a href="#dns_dnspromises_lookup_hostname_options"><code>dnsPromises.lookup()</code></a>. The value could be:</p> 962<ul> 963<li><code>ipv4first</code>: sets default <code>verbatim</code> <code>false</code>.</li> 964<li><code>verbatim</code>: sets default <code>verbatim</code> <code>true</code>.</li> 965</ul> 966<p>The default is <code>ipv4first</code> and <a href="#dns_dns_setdefaultresultorder_order"><code>dns.setDefaultResultOrder()</code></a> have higher 967priority than <a href="cli.html#cli_dns_result_order_order"><code>--dns-result-order</code></a>. When using <a href="worker_threads.html">worker threads</a>, 968<a href="#dns_dns_setdefaultresultorder_order"><code>dns.setDefaultResultOrder()</code></a> from the main thread won't affect the default 969dns orders in workers.</p> 970</section><section><h3><code>dns.setServers(servers)</code><span><a class="mark" href="#dns_dns_setservers_servers" id="dns_dns_setservers_servers">#</a></span></h3> 971<div class="api_metadata"> 972<span>Added in: v0.11.3</span> 973</div> 974<ul> 975<li><code>servers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted addresses</li> 976</ul> 977<p>Sets the IP address and port of servers to be used when performing DNS 978resolution. The <code>servers</code> argument is an array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted 979addresses. If the port is the IANA default DNS port (53) it can be omitted.</p> 980<pre><code class="language-js">dns.<span class="hljs-title function_">setServers</span>([ 981 <span class="hljs-string">'4.4.4.4'</span>, 982 <span class="hljs-string">'[2001:4860:4860::8888]'</span>, 983 <span class="hljs-string">'4.4.4.4:1053'</span>, 984 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 985]);</code></pre> 986<p>An error will be thrown if an invalid address is provided.</p> 987<p>The <code>dns.setServers()</code> method must not be called while a DNS query is in 988progress.</p> 989<p>The <a href="#dns_dns_setservers_servers"><code>dns.setServers()</code></a> method affects only <a href="#dns_dns_resolve_hostname_rrtype_callback"><code>dns.resolve()</code></a>, 990<code>dns.resolve*()</code> and <a href="#dns_dns_reverse_ip_callback"><code>dns.reverse()</code></a> (and specifically <em>not</em> 991<a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a>).</p> 992<p>This method works much like 993<a href="https://man7.org/linux/man-pages/man5/resolv.conf.5.html">resolve.conf</a>. 994That is, if attempting to resolve with the first server provided results in a 995<code>NOTFOUND</code> error, the <code>resolve()</code> method will <em>not</em> attempt to resolve with 996subsequent servers provided. Fallback DNS servers will only be used if the 997earlier ones time out or result in some other error.</p> 998</section><section><h3>DNS promises API<span><a class="mark" href="#dns_dns_promises_api" id="dns_dns_promises_api">#</a></span></h3> 999<div class="api_metadata"> 1000<details class="changelog"><summary>History</summary> 1001<table> 1002<tbody><tr><th>Version</th><th>Changes</th></tr> 1003<tr><td>v11.14.0, v10.17.0</td> 1004<td><p>This API is no longer experimental.</p></td></tr> 1005<tr><td>v10.6.0</td> 1006<td><p><span>Added in: v10.6.0</span></p></td></tr> 1007</tbody></table> 1008</details> 1009</div> 1010<p>The <code>dns.promises</code> API provides an alternative set of asynchronous DNS methods 1011that return <code>Promise</code> objects rather than using callbacks. The API is accessible 1012via <code>require('dns').promises</code>.</p> 1013<h4>Class: <code>dnsPromises.Resolver</code><span><a class="mark" href="#dns_class_dnspromises_resolver" id="dns_class_dnspromises_resolver">#</a></span></h4> 1014<div class="api_metadata"> 1015<span>Added in: v10.6.0</span> 1016</div> 1017<p>An independent resolver for DNS requests.</p> 1018<p>Creating a new resolver uses the default server settings. Setting 1019the servers used for a resolver using 1020<a href="#dns_dnspromises_setservers_servers"><code>resolver.setServers()</code></a> does not affect 1021other resolvers:</p> 1022<pre><code class="language-js"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">Resolver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>).<span class="hljs-property">promises</span>; 1023<span class="hljs-keyword">const</span> resolver = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Resolver</span>(); 1024resolver.<span class="hljs-title function_">setServers</span>([<span class="hljs-string">'4.4.4.4'</span>]); 1025 1026<span class="hljs-comment">// This request will use the server at 4.4.4.4, independent of global settings.</span> 1027resolver.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'example.org'</span>).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">addresses</span>) =></span> { 1028 <span class="hljs-comment">// ...</span> 1029}); 1030 1031<span class="hljs-comment">// Alternatively, the same code can be written using async-await style.</span> 1032(<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) { 1033 <span class="hljs-keyword">const</span> addresses = <span class="hljs-keyword">await</span> resolver.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'example.org'</span>); 1034})();</code></pre> 1035<p>The following methods from the <code>dnsPromises</code> API are available:</p> 1036<ul> 1037<li><a href="#dns_dnspromises_getservers"><code>resolver.getServers()</code></a></li> 1038<li><a href="#dns_dnspromises_resolve_hostname_rrtype"><code>resolver.resolve()</code></a></li> 1039<li><a href="#dns_dnspromises_resolve4_hostname_options"><code>resolver.resolve4()</code></a></li> 1040<li><a href="#dns_dnspromises_resolve6_hostname_options"><code>resolver.resolve6()</code></a></li> 1041<li><a href="#dns_dnspromises_resolveany_hostname"><code>resolver.resolveAny()</code></a></li> 1042<li><a href="#dns_dnspromises_resolvecaa_hostname"><code>resolver.resolveCaa()</code></a></li> 1043<li><a href="#dns_dnspromises_resolvecname_hostname"><code>resolver.resolveCname()</code></a></li> 1044<li><a href="#dns_dnspromises_resolvemx_hostname"><code>resolver.resolveMx()</code></a></li> 1045<li><a href="#dns_dnspromises_resolvenaptr_hostname"><code>resolver.resolveNaptr()</code></a></li> 1046<li><a href="#dns_dnspromises_resolvens_hostname"><code>resolver.resolveNs()</code></a></li> 1047<li><a href="#dns_dnspromises_resolveptr_hostname"><code>resolver.resolvePtr()</code></a></li> 1048<li><a href="#dns_dnspromises_resolvesoa_hostname"><code>resolver.resolveSoa()</code></a></li> 1049<li><a href="#dns_dnspromises_resolvesrv_hostname"><code>resolver.resolveSrv()</code></a></li> 1050<li><a href="#dns_dnspromises_resolvetxt_hostname"><code>resolver.resolveTxt()</code></a></li> 1051<li><a href="#dns_dnspromises_reverse_ip"><code>resolver.reverse()</code></a></li> 1052<li><a href="#dns_dnspromises_setservers_servers"><code>resolver.setServers()</code></a></li> 1053</ul> 1054<h4><code>resolver.cancel()</code><span><a class="mark" href="#dns_resolver_cancel_1" id="dns_resolver_cancel_1">#</a></span></h4> 1055<div class="api_metadata"> 1056<span>Added in: v14.17.0</span> 1057</div> 1058<p>Cancel all outstanding DNS queries made by this resolver. The corresponding 1059promises will be rejected with an error with code <code>ECANCELLED</code>.</p> 1060<h4><code>dnsPromises.getServers()</code><span><a class="mark" href="#dns_dnspromises_getservers" id="dns_dnspromises_getservers">#</a></span></h4> 1061<div class="api_metadata"> 1062<span>Added in: v10.6.0</span> 1063</div> 1064<ul> 1065<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1066</ul> 1067<p>Returns an array of IP address strings, formatted according to <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a>, 1068that are currently configured for DNS resolution. A string will include a port 1069section if a custom port is used.</p> 1070<!-- eslint-disable semi--> 1071<pre><code class="language-js">[ 1072 <span class="hljs-string">'4.4.4.4'</span>, 1073 <span class="hljs-string">'2001:4860:4860::8888'</span>, 1074 <span class="hljs-string">'4.4.4.4:1053'</span>, 1075 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 1076]</code></pre> 1077<h4><code>dnsPromises.lookup(hostname[, options])</code><span><a class="mark" href="#dns_dnspromises_lookup_hostname_options" id="dns_dnspromises_lookup_hostname_options">#</a></span></h4> 1078<div class="api_metadata"> 1079<span>Added in: v10.6.0</span> 1080</div> 1081<ul> 1082<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1083<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1084<ul> 1085<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The record family. Must be <code>4</code>, <code>6</code>, or <code>0</code>. The value 1086<code>0</code> indicates that IPv4 and IPv6 addresses are both returned. <strong>Default:</strong> 1087<code>0</code>.</li> 1088<li><code>hints</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> One or more <a href="#dns_supported_getaddrinfo_flags">supported <code>getaddrinfo</code> flags</a>. Multiple 1089flags may be passed by bitwise <code>OR</code>ing their values.</li> 1090<li><code>all</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>Promise</code> is resolved with all addresses in 1091an array. Otherwise, returns a single address. <strong>Default:</strong> <code>false</code>.</li> 1092<li><code>verbatim</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>Promise</code> is resolved with IPv4 and 1093IPv6 addresses in the order the DNS resolver returned them. When <code>false</code>, 1094IPv4 addresses are placed before IPv6 addresses. 1095<strong>Default:</strong> currently <code>false</code> (addresses are reordered) but this is 1096expected to change in the not too distant future. Default value is 1097configurable using <a href="#dns_dns_setdefaultresultorder_order"><code>dns.setDefaultResultOrder()</code></a> or 1098<a href="cli.html#cli_dns_result_order_order"><code>--dns-result-order</code></a>. New code should use <code>{ verbatim: true }</code>.</li> 1099</ul> 1100</li> 1101</ul> 1102<p>Resolves a host name (e.g. <code>'nodejs.org'</code>) into the first found A (IPv4) or 1103AAAA (IPv6) record. All <code>option</code> properties are optional. If <code>options</code> is an 1104integer, then it must be <code>4</code> or <code>6</code> – if <code>options</code> is not provided, then IPv4 1105and IPv6 addresses are both returned if found.</p> 1106<p>With the <code>all</code> option set to <code>true</code>, the <code>Promise</code> is resolved with <code>addresses</code> 1107being an array of objects with the properties <code>address</code> and <code>family</code>.</p> 1108<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> 1109is the error code. 1110Keep in mind that <code>err.code</code> will be set to <code>'ENOTFOUND'</code> not only when 1111the host name does not exist but also when the lookup fails in other ways 1112such as no available file descriptors.</p> 1113<p><a href="#dns_dnspromises_lookup_hostname_options"><code>dnsPromises.lookup()</code></a> does not necessarily have anything to do with the DNS 1114protocol. The implementation uses an operating system facility that can 1115associate names with addresses, and vice versa. This implementation can have 1116subtle but important consequences on the behavior of any Node.js program. Please 1117take some time to consult the <a href="#dns_implementation_considerations">Implementation considerations section</a> before 1118using <code>dnsPromises.lookup()</code>.</p> 1119<p>Example usage:</p> 1120<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>); 1121<span class="hljs-keyword">const</span> dnsPromises = dns.<span class="hljs-property">promises</span>; 1122<span class="hljs-keyword">const</span> options = { 1123 <span class="hljs-attr">family</span>: <span class="hljs-number">6</span>, 1124 <span class="hljs-attr">hints</span>: dns.<span class="hljs-property">ADDRCONFIG</span> | dns.<span class="hljs-property">V4MAPPED</span>, 1125}; 1126 1127dnsPromises.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1128 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'address: %j family: IPv%s'</span>, result.<span class="hljs-property">address</span>, result.<span class="hljs-property">family</span>); 1129 <span class="hljs-comment">// address: "2606:2800:220:1:248:1893:25c8:1946" family: IPv6</span> 1130}); 1131 1132<span class="hljs-comment">// When options.all is true, the result will be an Array.</span> 1133options.<span class="hljs-property">all</span> = <span class="hljs-literal">true</span>; 1134dnsPromises.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1135 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'addresses: %j'</span>, result); 1136 <span class="hljs-comment">// addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]</span> 1137});</code></pre> 1138<h4><code>dnsPromises.lookupService(address, port)</code><span><a class="mark" href="#dns_dnspromises_lookupservice_address_port" id="dns_dnspromises_lookupservice_address_port">#</a></span></h4> 1139<div class="api_metadata"> 1140<span>Added in: v10.6.0</span> 1141</div> 1142<ul> 1143<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1144<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1145</ul> 1146<p>Resolves the given <code>address</code> and <code>port</code> into a host name and service using 1147the operating system's underlying <code>getnameinfo</code> implementation.</p> 1148<p>If <code>address</code> is not a valid IP address, a <code>TypeError</code> will be thrown. 1149The <code>port</code> will be coerced to a number. If it is not a legal port, a <code>TypeError</code> 1150will be thrown.</p> 1151<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> 1152is the error code.</p> 1153<pre><code class="language-js"><span class="hljs-keyword">const</span> dnsPromises = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dns'</span>).<span class="hljs-property">promises</span>; 1154dnsPromises.<span class="hljs-title function_">lookupService</span>(<span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-number">22</span>).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1155 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(result.<span class="hljs-property">hostname</span>, result.<span class="hljs-property">service</span>); 1156 <span class="hljs-comment">// Prints: localhost ssh</span> 1157});</code></pre> 1158<h4><code>dnsPromises.resolve(hostname[, rrtype])</code><span><a class="mark" href="#dns_dnspromises_resolve_hostname_rrtype" id="dns_dnspromises_resolve_hostname_rrtype">#</a></span></h4> 1159<div class="api_metadata"> 1160<span>Added in: v10.6.0</span> 1161</div> 1162<ul> 1163<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 1164<li><code>rrtype</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Resource record type. <strong>Default:</strong> <code>'A'</code>.</li> 1165</ul> 1166<p>Uses the DNS protocol to resolve a host name (e.g. <code>'nodejs.org'</code>) into an array 1167of the resource records. When successful, the <code>Promise</code> is resolved with an 1168array of resource records. The type and structure of individual results vary 1169based on <code>rrtype</code>:</p> 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253<table><thead><tr><th><code>rrtype</code></th><th><code>records</code> contains</th><th>Result type</th><th>Shorthand method</th></tr></thead><tbody><tr><td><code>'A'</code></td><td>IPv4 addresses (default)</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dnspromises_resolve4_hostname_options"><code>dnsPromises.resolve4()</code></a></td></tr><tr><td><code>'AAAA'</code></td><td>IPv6 addresses</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dnspromises_resolve6_hostname_options"><code>dnsPromises.resolve6()</code></a></td></tr><tr><td><code>'ANY'</code></td><td>any records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dnspromises_resolveany_hostname"><code>dnsPromises.resolveAny()</code></a></td></tr><tr><td><code>'CAA'</code></td><td>CA authorization records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dnspromises_resolvecaa_hostname"><code>dnsPromises.resolveCaa()</code></a></td></tr><tr><td><code>'CNAME'</code></td><td>canonical name records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dnspromises_resolvecname_hostname"><code>dnsPromises.resolveCname()</code></a></td></tr><tr><td><code>'MX'</code></td><td>mail exchange records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dnspromises_resolvemx_hostname"><code>dnsPromises.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>name authority pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dnspromises_resolvenaptr_hostname"><code>dnsPromises.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td>name server records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dnspromises_resolvens_hostname"><code>dnsPromises.resolveNs()</code></a></td></tr><tr><td><code>'PTR'</code></td><td>pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dns_dnspromises_resolveptr_hostname"><code>dnsPromises.resolvePtr()</code></a></td></tr><tr><td><code>'SOA'</code></td><td>start of authority records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dnspromises_resolvesoa_hostname"><code>dnsPromises.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>service records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dns_dnspromises_resolvesrv_hostname"><code>dnsPromises.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>text records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></td><td><a href="#dns_dnspromises_resolvetxt_hostname"><code>dnsPromises.resolveTxt()</code></a></td></tr></tbody></table> 1254<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> 1255is one of the <a href="#dns_error_codes">DNS error codes</a>.</p> 1256<h4><code>dnsPromises.resolve4(hostname[, options])</code><span><a class="mark" href="#dns_dnspromises_resolve4_hostname_options" id="dns_dnspromises_resolve4_hostname_options">#</a></span></h4> 1257<div class="api_metadata"> 1258<span>Added in: v10.6.0</span> 1259</div> 1260<ul> 1261<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 1262<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1263<ul> 1264<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 1265When <code>true</code>, the <code>Promise</code> is resolved with an array of 1266<code>{ address: '1.2.3.4', ttl: 60 }</code> objects rather than an array of strings, 1267with the TTL expressed in seconds.</li> 1268</ul> 1269</li> 1270</ul> 1271<p>Uses the DNS protocol to resolve IPv4 addresses (<code>A</code> records) for the 1272<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of IPv4 1273addresses (e.g. <code>['74.125.79.104', '74.125.79.105', '74.125.79.106']</code>).</p> 1274<h4><code>dnsPromises.resolve6(hostname[, options])</code><span><a class="mark" href="#dns_dnspromises_resolve6_hostname_options" id="dns_dnspromises_resolve6_hostname_options">#</a></span></h4> 1275<div class="api_metadata"> 1276<span>Added in: v10.6.0</span> 1277</div> 1278<ul> 1279<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 1280<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1281<ul> 1282<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 1283When <code>true</code>, the <code>Promise</code> is resolved with an array of 1284<code>{ address: '0:1:2:3:4:5:6:7', ttl: 60 }</code> objects rather than an array of 1285strings, with the TTL expressed in seconds.</li> 1286</ul> 1287</li> 1288</ul> 1289<p>Uses the DNS protocol to resolve IPv6 addresses (<code>AAAA</code> records) for the 1290<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of IPv6 1291addresses.</p> 1292<h4><code>dnsPromises.resolveAny(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolveany_hostname" id="dns_dnspromises_resolveany_hostname">#</a></span></h4> 1293<div class="api_metadata"> 1294<span>Added in: v10.6.0</span> 1295</div> 1296<ul> 1297<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1298</ul> 1299<p>Uses the DNS protocol to resolve all records (also known as <code>ANY</code> or <code>*</code> query). 1300On success, the <code>Promise</code> is resolved with an array containing various types of 1301records. Each object has a property <code>type</code> that indicates the type of the 1302current record. And depending on the <code>type</code>, additional properties will be 1303present on the object:</p> 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353<table><thead><tr><th>Type</th><th>Properties</th></tr></thead><tbody><tr><td><code>'A'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'AAAA'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'CNAME'</code></td><td><code>value</code></td></tr><tr><td><code>'MX'</code></td><td>Refer to <a href="#dns_dnspromises_resolvemx_hostname"><code>dnsPromises.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>Refer to <a href="#dns_dnspromises_resolvenaptr_hostname"><code>dnsPromises.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td><code>value</code></td></tr><tr><td><code>'PTR'</code></td><td><code>value</code></td></tr><tr><td><code>'SOA'</code></td><td>Refer to <a href="#dns_dnspromises_resolvesoa_hostname"><code>dnsPromises.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>Refer to <a href="#dns_dnspromises_resolvesrv_hostname"><code>dnsPromises.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>This type of record contains an array property called <code>entries</code> which refers to <a href="#dns_dnspromises_resolvetxt_hostname"><code>dnsPromises.resolveTxt()</code></a>, e.g. <code>{ entries: ['...'], type: 'TXT' }</code></td></tr></tbody></table> 1354<p>Here is an example of the result object:</p> 1355<!-- eslint-disable semi --> 1356<pre><code class="language-js">[ { <span class="hljs-attr">type</span>: <span class="hljs-string">'A'</span>, <span class="hljs-attr">address</span>: <span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-attr">ttl</span>: <span class="hljs-number">299</span> }, 1357 { <span class="hljs-attr">type</span>: <span class="hljs-string">'CNAME'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'example.com'</span> }, 1358 { <span class="hljs-attr">type</span>: <span class="hljs-string">'MX'</span>, <span class="hljs-attr">exchange</span>: <span class="hljs-string">'alt4.aspmx.l.example.com'</span>, <span class="hljs-attr">priority</span>: <span class="hljs-number">50</span> }, 1359 { <span class="hljs-attr">type</span>: <span class="hljs-string">'NS'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'ns1.example.com'</span> }, 1360 { <span class="hljs-attr">type</span>: <span class="hljs-string">'TXT'</span>, <span class="hljs-attr">entries</span>: [ <span class="hljs-string">'v=spf1 include:_spf.example.com ~all'</span> ] }, 1361 { <span class="hljs-attr">type</span>: <span class="hljs-string">'SOA'</span>, 1362 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns1.example.com'</span>, 1363 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'admin.example.com'</span>, 1364 <span class="hljs-attr">serial</span>: <span class="hljs-number">156696742</span>, 1365 <span class="hljs-attr">refresh</span>: <span class="hljs-number">900</span>, 1366 <span class="hljs-attr">retry</span>: <span class="hljs-number">900</span>, 1367 <span class="hljs-attr">expire</span>: <span class="hljs-number">1800</span>, 1368 <span class="hljs-attr">minttl</span>: <span class="hljs-number">60</span> } ]</code></pre> 1369<h4><code>dnsPromises.resolveCaa(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvecaa_hostname" id="dns_dnspromises_resolvecaa_hostname">#</a></span></h4> 1370<div class="api_metadata"> 1371<span>Added in: v14.17.0</span> 1372</div> 1373<ul> 1374<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1375</ul> 1376<p>Uses the DNS protocol to resolve <code>CAA</code> records for the <code>hostname</code>. On success, 1377the <code>Promise</code> is resolved with an array of objects containing available 1378certification authority authorization records available for the <code>hostname</code> 1379(e.g. <code>[{critical: 0, iodef: 'mailto:pki@example.com'},{critical: 128, issue: 'pki.example.com'}]</code>).</p> 1380<h4><code>dnsPromises.resolveCname(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvecname_hostname" id="dns_dnspromises_resolvecname_hostname">#</a></span></h4> 1381<div class="api_metadata"> 1382<span>Added in: v10.6.0</span> 1383</div> 1384<ul> 1385<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1386</ul> 1387<p>Uses the DNS protocol to resolve <code>CNAME</code> records for the <code>hostname</code>. On success, 1388the <code>Promise</code> is resolved with an array of canonical name records available for 1389the <code>hostname</code> (e.g. <code>['bar.example.com']</code>).</p> 1390<h4><code>dnsPromises.resolveMx(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvemx_hostname" id="dns_dnspromises_resolvemx_hostname">#</a></span></h4> 1391<div class="api_metadata"> 1392<span>Added in: v10.6.0</span> 1393</div> 1394<ul> 1395<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1396</ul> 1397<p>Uses the DNS protocol to resolve mail exchange records (<code>MX</code> records) for the 1398<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of objects 1399containing both a <code>priority</code> and <code>exchange</code> property (e.g. 1400<code>[{priority: 10, exchange: 'mx.example.com'}, ...]</code>).</p> 1401<h4><code>dnsPromises.resolveNaptr(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvenaptr_hostname" id="dns_dnspromises_resolvenaptr_hostname">#</a></span></h4> 1402<div class="api_metadata"> 1403<span>Added in: v10.6.0</span> 1404</div> 1405<ul> 1406<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1407</ul> 1408<p>Uses the DNS protocol to resolve regular expression based records (<code>NAPTR</code> 1409records) for the <code>hostname</code>. On success, the <code>Promise</code> is resolved with an array 1410of objects with the following properties:</p> 1411<ul> 1412<li><code>flags</code></li> 1413<li><code>service</code></li> 1414<li><code>regexp</code></li> 1415<li><code>replacement</code></li> 1416<li><code>order</code></li> 1417<li><code>preference</code></li> 1418</ul> 1419<!-- eslint-skip --> 1420<pre><code class="language-js">{ 1421 <span class="hljs-attr">flags</span>: <span class="hljs-string">'s'</span>, 1422 <span class="hljs-attr">service</span>: <span class="hljs-string">'SIP+D2U'</span>, 1423 <span class="hljs-attr">regexp</span>: <span class="hljs-string">''</span>, 1424 <span class="hljs-attr">replacement</span>: <span class="hljs-string">'_sip._udp.example.com'</span>, 1425 <span class="hljs-attr">order</span>: <span class="hljs-number">30</span>, 1426 <span class="hljs-attr">preference</span>: <span class="hljs-number">100</span> 1427}</code></pre> 1428<h4><code>dnsPromises.resolveNs(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvens_hostname" id="dns_dnspromises_resolvens_hostname">#</a></span></h4> 1429<div class="api_metadata"> 1430<span>Added in: v10.6.0</span> 1431</div> 1432<ul> 1433<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1434</ul> 1435<p>Uses the DNS protocol to resolve name server records (<code>NS</code> records) for the 1436<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of name server 1437records available for <code>hostname</code> (e.g. 1438<code>['ns1.example.com', 'ns2.example.com']</code>).</p> 1439<h4><code>dnsPromises.resolvePtr(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolveptr_hostname" id="dns_dnspromises_resolveptr_hostname">#</a></span></h4> 1440<div class="api_metadata"> 1441<span>Added in: v10.6.0</span> 1442</div> 1443<ul> 1444<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1445</ul> 1446<p>Uses the DNS protocol to resolve pointer records (<code>PTR</code> records) for the 1447<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of strings 1448containing the reply records.</p> 1449<h4><code>dnsPromises.resolveSoa(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvesoa_hostname" id="dns_dnspromises_resolvesoa_hostname">#</a></span></h4> 1450<div class="api_metadata"> 1451<span>Added in: v10.6.0</span> 1452</div> 1453<ul> 1454<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1455</ul> 1456<p>Uses the DNS protocol to resolve a start of authority record (<code>SOA</code> record) for 1457the <code>hostname</code>. On success, the <code>Promise</code> is resolved with an object with the 1458following properties:</p> 1459<ul> 1460<li><code>nsname</code></li> 1461<li><code>hostmaster</code></li> 1462<li><code>serial</code></li> 1463<li><code>refresh</code></li> 1464<li><code>retry</code></li> 1465<li><code>expire</code></li> 1466<li><code>minttl</code></li> 1467</ul> 1468<!-- eslint-skip --> 1469<pre><code class="language-js">{ 1470 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns.example.com'</span>, 1471 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'root.example.com'</span>, 1472 <span class="hljs-attr">serial</span>: <span class="hljs-number">2013101809</span>, 1473 <span class="hljs-attr">refresh</span>: <span class="hljs-number">10000</span>, 1474 <span class="hljs-attr">retry</span>: <span class="hljs-number">2400</span>, 1475 <span class="hljs-attr">expire</span>: <span class="hljs-number">604800</span>, 1476 <span class="hljs-attr">minttl</span>: <span class="hljs-number">3600</span> 1477}</code></pre> 1478<h4><code>dnsPromises.resolveSrv(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvesrv_hostname" id="dns_dnspromises_resolvesrv_hostname">#</a></span></h4> 1479<div class="api_metadata"> 1480<span>Added in: v10.6.0</span> 1481</div> 1482<ul> 1483<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1484</ul> 1485<p>Uses the DNS protocol to resolve service records (<code>SRV</code> records) for the 1486<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of objects with 1487the following properties:</p> 1488<ul> 1489<li><code>priority</code></li> 1490<li><code>weight</code></li> 1491<li><code>port</code></li> 1492<li><code>name</code></li> 1493</ul> 1494<!-- eslint-skip --> 1495<pre><code class="language-js">{ 1496 <span class="hljs-attr">priority</span>: <span class="hljs-number">10</span>, 1497 <span class="hljs-attr">weight</span>: <span class="hljs-number">5</span>, 1498 <span class="hljs-attr">port</span>: <span class="hljs-number">21223</span>, 1499 <span class="hljs-attr">name</span>: <span class="hljs-string">'service.example.com'</span> 1500}</code></pre> 1501<h4><code>dnsPromises.resolveTxt(hostname)</code><span><a class="mark" href="#dns_dnspromises_resolvetxt_hostname" id="dns_dnspromises_resolvetxt_hostname">#</a></span></h4> 1502<div class="api_metadata"> 1503<span>Added in: v10.6.0</span> 1504</div> 1505<ul> 1506<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1507</ul> 1508<p>Uses the DNS protocol to resolve text queries (<code>TXT</code> records) for the 1509<code>hostname</code>. On success, the <code>Promise</code> is resolved with a two-dimensional array 1510of the text records available for <code>hostname</code> (e.g. 1511<code>[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]</code>). Each sub-array contains TXT chunks of 1512one record. Depending on the use case, these could be either joined together or 1513treated separately.</p> 1514<h4><code>dnsPromises.reverse(ip)</code><span><a class="mark" href="#dns_dnspromises_reverse_ip" id="dns_dnspromises_reverse_ip">#</a></span></h4> 1515<div class="api_metadata"> 1516<span>Added in: v10.6.0</span> 1517</div> 1518<ul> 1519<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1520</ul> 1521<p>Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an 1522array of host names.</p> 1523<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#errors_class_error"><code>Error</code></a> object, where <code>err.code</code> 1524is one of the <a href="#dns_error_codes">DNS error codes</a>.</p> 1525<h4><code>dnsPromises.setDefaultResultOrder(order)</code><span><a class="mark" href="#dns_dnspromises_setdefaultresultorder_order" id="dns_dnspromises_setdefaultresultorder_order">#</a></span></h4> 1526<div class="api_metadata"> 1527<span>Added in: v14.18.0</span> 1528</div> 1529<ul> 1530<li><code>order</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> must be <code>'ipv4first'</code> or <code>'verbatim'</code>.</li> 1531</ul> 1532<p>Set the default value of <code>verbatim</code> in <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> and 1533<a href="#dns_dnspromises_lookup_hostname_options"><code>dnsPromises.lookup()</code></a>. The value could be:</p> 1534<ul> 1535<li><code>ipv4first</code>: sets default <code>verbatim</code> <code>false</code>.</li> 1536<li><code>verbatim</code>: sets default <code>verbatim</code> <code>true</code>.</li> 1537</ul> 1538<p>The default is <code>ipv4first</code> and <a href="#dns_dnspromises_setdefaultresultorder_order"><code>dnsPromises.setDefaultResultOrder()</code></a> have 1539higher priority than <a href="cli.html#cli_dns_result_order_order"><code>--dns-result-order</code></a>. When using <a href="worker_threads.html">worker threads</a>, 1540<a href="#dns_dnspromises_setdefaultresultorder_order"><code>dnsPromises.setDefaultResultOrder()</code></a> from the main thread won't affect the 1541default dns orders in workers.</p> 1542<h4><code>dnsPromises.setServers(servers)</code><span><a class="mark" href="#dns_dnspromises_setservers_servers" id="dns_dnspromises_setservers_servers">#</a></span></h4> 1543<div class="api_metadata"> 1544<span>Added in: v10.6.0</span> 1545</div> 1546<ul> 1547<li><code>servers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted addresses</li> 1548</ul> 1549<p>Sets the IP address and port of servers to be used when performing DNS 1550resolution. The <code>servers</code> argument is an array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted 1551addresses. If the port is the IANA default DNS port (53) it can be omitted.</p> 1552<pre><code class="language-js">dnsPromises.<span class="hljs-title function_">setServers</span>([ 1553 <span class="hljs-string">'4.4.4.4'</span>, 1554 <span class="hljs-string">'[2001:4860:4860::8888]'</span>, 1555 <span class="hljs-string">'4.4.4.4:1053'</span>, 1556 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 1557]);</code></pre> 1558<p>An error will be thrown if an invalid address is provided.</p> 1559<p>The <code>dnsPromises.setServers()</code> method must not be called while a DNS query is in 1560progress.</p> 1561<p>This method works much like 1562<a href="https://man7.org/linux/man-pages/man5/resolv.conf.5.html">resolve.conf</a>. 1563That is, if attempting to resolve with the first server provided results in a 1564<code>NOTFOUND</code> error, the <code>resolve()</code> method will <em>not</em> attempt to resolve with 1565subsequent servers provided. Fallback DNS servers will only be used if the 1566earlier ones time out or result in some other error.</p> 1567</section><section><h3>Error codes<span><a class="mark" href="#dns_error_codes" id="dns_error_codes">#</a></span></h3> 1568<p>Each DNS query can return one of the following error codes:</p> 1569<ul> 1570<li><code>dns.NODATA</code>: DNS server returned answer with no data.</li> 1571<li><code>dns.FORMERR</code>: DNS server claims query was misformatted.</li> 1572<li><code>dns.SERVFAIL</code>: DNS server returned general failure.</li> 1573<li><code>dns.NOTFOUND</code>: Domain name not found.</li> 1574<li><code>dns.NOTIMP</code>: DNS server does not implement requested operation.</li> 1575<li><code>dns.REFUSED</code>: DNS server refused query.</li> 1576<li><code>dns.BADQUERY</code>: Misformatted DNS query.</li> 1577<li><code>dns.BADNAME</code>: Misformatted host name.</li> 1578<li><code>dns.BADFAMILY</code>: Unsupported address family.</li> 1579<li><code>dns.BADRESP</code>: Misformatted DNS reply.</li> 1580<li><code>dns.CONNREFUSED</code>: Could not contact DNS servers.</li> 1581<li><code>dns.TIMEOUT</code>: Timeout while contacting DNS servers.</li> 1582<li><code>dns.EOF</code>: End of file.</li> 1583<li><code>dns.FILE</code>: Error reading file.</li> 1584<li><code>dns.NOMEM</code>: Out of memory.</li> 1585<li><code>dns.DESTRUCTION</code>: Channel is being destroyed.</li> 1586<li><code>dns.BADSTR</code>: Misformatted string.</li> 1587<li><code>dns.BADFLAGS</code>: Illegal flags specified.</li> 1588<li><code>dns.NONAME</code>: Given host name is not numeric.</li> 1589<li><code>dns.BADHINTS</code>: Illegal hints flags specified.</li> 1590<li><code>dns.NOTINITIALIZED</code>: c-ares library initialization not yet performed.</li> 1591<li><code>dns.LOADIPHLPAPI</code>: Error loading <code>iphlpapi.dll</code>.</li> 1592<li><code>dns.ADDRGETNETWORKPARAMS</code>: Could not find <code>GetNetworkParams</code> function.</li> 1593<li><code>dns.CANCELLED</code>: DNS query cancelled.</li> 1594</ul> 1595</section><section><h3>Implementation considerations<span><a class="mark" href="#dns_implementation_considerations" id="dns_implementation_considerations">#</a></span></h3> 1596<p>Although <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> and the various <code>dns.resolve*()/dns.reverse()</code> 1597functions have the same goal of associating a network name with a network 1598address (or vice versa), their behavior is quite different. These differences 1599can have subtle but significant consequences on the behavior of Node.js 1600programs.</p> 1601<h4><code>dns.lookup()</code><span><a class="mark" href="#dns_dns_lookup" id="dns_dns_lookup">#</a></span></h4> 1602<p>Under the hood, <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> uses the same operating system facilities 1603as most other programs. For instance, <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> will almost always 1604resolve a given name the same way as the <code>ping</code> command. On most POSIX-like 1605operating systems, the behavior of the <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> function can be 1606modified by changing settings in <a href="http://man7.org/linux/man-pages/man5/nsswitch.conf.5.html"><code>nsswitch.conf(5)</code></a> and/or <a href="http://man7.org/linux/man-pages/man5/resolv.conf.5.html"><code>resolv.conf(5)</code></a>, 1607but changing these files will change the behavior of all other 1608programs running on the same operating system.</p> 1609<p>Though the call to <code>dns.lookup()</code> will be asynchronous from JavaScript's 1610perspective, it is implemented as a synchronous call to <a href="http://man7.org/linux/man-pages/man3/getaddrinfo.3.html"><code>getaddrinfo(3)</code></a> that runs 1611on libuv's threadpool. This can have surprising negative performance 1612implications for some applications, see the <a href="cli.html#cli_uv_threadpool_size_size"><code>UV_THREADPOOL_SIZE</code></a> 1613documentation for more information.</p> 1614<p>Various networking APIs will call <code>dns.lookup()</code> internally to resolve 1615host names. If that is an issue, consider resolving the host name to an address 1616using <code>dns.resolve()</code> and using the address instead of a host name. Also, some 1617networking APIs (such as <a href="net.html#net_socket_connect_options_connectlistener"><code>socket.connect()</code></a> and <a href="dgram.html#dgram_dgram_createsocket_options_callback"><code>dgram.createSocket()</code></a>) 1618allow the default resolver, <code>dns.lookup()</code>, to be replaced.</p> 1619<h4><code>dns.resolve()</code>, <code>dns.resolve*()</code> and <code>dns.reverse()</code><span><a class="mark" href="#dns_dns_resolve_dns_resolve_and_dns_reverse" id="dns_dns_resolve_dns_resolve_and_dns_reverse">#</a></span></h4> 1620<p>These functions are implemented quite differently than <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a>. They 1621do not use <a href="http://man7.org/linux/man-pages/man3/getaddrinfo.3.html"><code>getaddrinfo(3)</code></a> and they <em>always</em> perform a DNS query on the 1622network. This network communication is always done asynchronously, and does not 1623use libuv's threadpool.</p> 1624<p>As a result, these functions cannot have the same negative impact on other 1625processing that happens on libuv's threadpool that <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> can have.</p> 1626<p>They do not use the same set of configuration files than what <a href="#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a> 1627uses. For instance, <em>they do not use the configuration from <code>/etc/hosts</code></em>.</p></section> 1628 <!-- API END --> 1629 </div> 1630 </div> 1631 </div> 1632 <script> 1633 'use strict'; 1634 { 1635 const kCustomPreference = 'customDarkTheme'; 1636 const userSettings = sessionStorage.getItem(kCustomPreference); 1637 const themeToggleButton = document.getElementById('theme-toggle-btn'); 1638 if (userSettings === null && window.matchMedia) { 1639 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 1640 if ('onchange' in mq) { 1641 function mqChangeListener(e) { 1642 document.body.classList.toggle('dark-mode', e.matches); 1643 } 1644 mq.addEventListener('change', mqChangeListener); 1645 if (themeToggleButton) { 1646 themeToggleButton.addEventListener('click', function() { 1647 mq.removeEventListener('change', mqChangeListener); 1648 }, { once: true }); 1649 } 1650 } 1651 if (mq.matches) { 1652 document.body.classList.add('dark-mode'); 1653 } 1654 } else if (userSettings === 'true') { 1655 document.body.classList.add('dark-mode'); 1656 } 1657 if (themeToggleButton) { 1658 themeToggleButton.hidden = false; 1659 themeToggleButton.addEventListener('click', function() { 1660 sessionStorage.setItem( 1661 kCustomPreference, 1662 document.body.classList.toggle('dark-mode') 1663 ); 1664 }); 1665 } 1666 } 1667 </script> 1668</body> 1669</html> 1670